#![warn(clippy::transmutes_expressible_as_ptr_casts)] // These two warnings currently cover the cases transmutes_expressible_as_ptr_casts // would otherwise be responsible for #![warn(clippy::useless_transmute)] #![warn(clippy::transmute_ptr_to_ptr)] #![allow(unused, clippy::borrow_as_ptr)] use std::mem::{size_of, transmute}; // rustc_hir_analysis::check::cast contains documentation about when a cast `e as U` is // valid, which we quote from below. fn main() { // We should see an error message for each transmute, and no error messages for // the casts, since the casts are the recommended fixes. // e is an integer and U is *U_0, while U_0: Sized; addr-ptr-cast let _ptr_i32_transmute = unsafe { transmute::<usize, *const i32>(usize::MAX) }; let ptr_i32 = usize::MAX as *const i32; // e has type *T, U is *U_0, and either U_0: Sized ... let _ptr_i8_transmute = unsafe { transmute::<*const i32, *const i8>(ptr_i32) }; let _ptr_i8 = ptr_i32 as *const i8; let slice_ptr = &[0, 1, 2, 3] as *const [i32]; // ... or pointer_kind(T) = pointer_kind(U_0); ptr-ptr-cast let _ptr_to_unsized_transmute = unsafe { transmute::<*const [i32], *const [u32]>(slice_ptr) }; let _ptr_to_unsized = slice_ptr as *const [u32]; // TODO: We could try testing vtable casts here too, but maybe // we should wait until std::raw::TraitObject is stabilized? // e has type *T and U is a numeric type, while T: Sized; ptr-addr-cast let _usize_from_int_ptr_transmute = unsafe { transmute::<*const i32, usize>(ptr_i32) }; let _usize_from_int_ptr = ptr_i32 as usize; let array_ref: &[i32; 4] = &[1, 2, 3, 4]; // e has type &[T; n] and U is *const T; array-ptr-cast let _array_ptr_transmute = unsafe { transmute::<&[i32; 4], *const [i32; 4]>(array_ref) }; let _array_ptr = array_ref as *const [i32; 4]; fn foo(_: usize) -> u8 { 42 } // e is a function pointer type and U has type *T, while T: Sized; fptr-ptr-cast let _usize_ptr_transmute = unsafe { transmute::<fn(usize) -> u8, *const usize>(foo) }; let _usize_ptr_transmute = foo as *const usize; // e is a function pointer type and U is an integer; fptr-addr-cast let _usize_from_fn_ptr_transmute = unsafe { transmute::<fn(usize) -> u8, usize>(foo) }; let _usize_from_fn_ptr = foo as *const usize; let _usize_from_ref = unsafe { transmute::<*const u32, usize>(&1u32) }; } // If a ref-to-ptr cast of this form where the pointer type points to a type other // than the referenced type, calling `CastCheck::do_check` has been observed to // cause an ICE error message. `do_check` is currently called inside the // `transmutes_expressible_as_ptr_casts` check, but other, more specific lints // currently prevent it from being called in these cases. This test is meant to // fail if the ordering of the checks ever changes enough to cause these cases to // fall through into `do_check`. fn trigger_do_check_to_emit_error(in_param: &[i32; 1]) -> *const u8 { unsafe { transmute::<&[i32; 1], *const u8>(in_param) } } #[repr(C)] struct Single(u64); #[repr(C)] struct Pair(u32, u32); fn cannot_be_expressed_as_pointer_cast(in_param: Single) -> Pair { assert_eq!(size_of::<Single>(), size_of::<Pair>()); unsafe { transmute::<Single, Pair>(in_param) } } fn issue_10449() { fn f() {} let _x: u8 = unsafe { *std::mem::transmute::<fn(), *const u8>(f) }; }